arXiv subjects

Mahesh Kumar

Publications and source records attributed to Mahesh Kumar.

At least 19 recordsLinked to original sources

arXiv2026

Quantifying biofilm-virulence index to predict antifungal resistance in Candida albicans

Candida albicans is a commensal microorganism that causes opportunistic infections, such as oral candidiasis, vaginitis affecting females, newborns, and immunocompromised patients. Biofilm formation can lead to a commensal organism becoming a life-threatening organism by introducing antifungal resistance. The experiment we did combines crystal violet staining for biofilm biomass and CFU counts to statistically construct an additive BVI model by analysing the experimental data. Our study on the data proposes a Biofilm-Virulence Index (BVI) as a novel and quantitative parameter for assessing antifungal drug resistance in Candida albicans. The effect of the drugs on inhibition zone diameter is twofold, first, linear increase with time during early biofilm formation, second, stabilizing in later phases and correlating directly with virulence. Most BVI values remained in the mild infection range, indicating successful virulence reduction by antifungal drugs. The BVI model model combines the study of biofilm and viable cell count in a single parameter. So, this makes comparison between samples easier during biofilm analysis. Findings suggest that combination of CFU and biofilm measurement may improve interpretation of antifungal response in Candida albicans. This approach could be useful in future experimental studies investigating biofilm associated resistance.

q-bio.OT↗

arXiv2026

FinReflectKG -- HalluBench: GraphRAG Hallucination Benchmark for Financial Question Answering Systems

As organizations increasingly integrate AI-powered question-answering systems into financial information systems for compliance, risk assessment, and decision support, ensuring the factual accuracy of AI-generated outputs becomes a critical engineering challenge. Current Knowledge Graph (KG)-augmented QA systems lack systematic mechanisms to detect hallucinations - factually incorrect outputs that undermine reliability and user trust. We introduce FinBench-QA-Hallucination, a benchmark for evaluating hallucination detection methods in KG-augmented financial QA over SEC 10-K filings. The dataset contains 755 annotated examples from 300 pages, each labeled for groundedness using a conservative evidence-linkage protocol requiring support from both textual chunks and extracted relational triplets. We evaluate six detection approaches - LLM judges, fine-tuned classifiers, Natural Language Inference (NLI) models, span detectors, and embedding-based methods under two conditions: with and without KG triplets. Results show that LLM-based judges and embedding approaches achieve the highest performance (F1: 0.82-0.86) under clean conditions. However, most methods degrade significantly when noisy triplets are introduced, with Matthews Correlation Coefficient (MCC) dropping 44-84 percent, while embedding methods remain relatively robust with only 9 percent degradation. Statistical tests (Cochran's Q and McNemar) confirm significant performance differences (p < 0.001). Our findings highlight vulnerabilities in current KG-augmented systems and provide insights for building reliable financial information systems, where hallucinations can lead to regulatory violations and flawed decisions. The benchmark also offers a framework for integrating AI reliability evaluation into information system design across other high-stakes domains such as healthcare, legal, and government.

cs.CL↗

arXiv2026

Stochastic Evolution of Galactic Star Formation with Halo Coupling, AGN Quenching and Hopf Bifurcation Dynamics

We present a computational framework for galactic evolution based on a coupled stochastic nonlinear oscillator, implemented with the \textbf{Stochastic Hopf Engine}. Gas density ($G$) and star formation rate ($S$) co-evolve through a supercritical Hopf bifurcation, capturing the transition from quiescent stability to merger-driven starbursts. Scatter in dark matter halo properties, modeled as multiplicative noise via the \textbf{Euler--Maruyama method}, broadens the bifurcation into a regime where noise-induced bursts occur below the deterministic threshold. Simulations reveal a periodic signature, the \textbf{Galactic Heartbeat}, emerging as a deterministic limit cycle validated by the \textbf{data3} resonance peak in the star-formation spectrum. A radial reduction yields an effective \textbf{Fokker--Planck equation} for burst amplitude; its stationary solution matches numerical PDFs, providing statistical closure. Including differential shear $\Omega(r)$ and spatially varying bifurcation fields reproduces spiral morphologies and AGN-driven quenching. Driving the growth parameter sub-critical ($r_{agn} < 0$) yields ``Red and Dead'' cores via attractor collapse. Dark matter halo scatter suppresses mean star formation while enhancing intermittency, offering a minimal yet interpretable framework linking local feedback and global potentials to macroscopic galactic evolution.

astro-ph.GA↗

arXiv2025

Tunable resonant Raman scattering with temperature in vertically aligned 2H-SnS2

Two-dimensional semiconducting materials have a wide range of applications in various fields due to their excellent properties and rich physics. Here, we report a detailed investigation of the temperature dependent Raman and Photoluminescence measurements on the vertically aligned 2H-SnS2 grown by CVD method. Our results established the tunability of the resonant Raman scattering with varying temperature, i.e. a crossover between resonance and non-resonance conditions for the current system. We also discussed the temperature as well as laser power dependence of the low frequency asymmetric Raman mode which is interlayer shear mode. Temperature dependence of the intensity of the phonon modes also manifests the tunability of the resonant Raman scattering with temperature. Our temperature dependent Photoluminescence measurement shows the strong temperature dependence of the excitonic peaks which is confirmed with laser power dependence of the Photoluminescence measurement at room temperature. Our investigation may help to design and fabricate devices based on vertically aligned 2H-SnS2 and other similar materials in future.

cond-mat.mtrl-sci↗

arXiv2024

Interferometric Single-Shot Parity Measurement in an InAs-Al Hybrid Device

The fusion of non-Abelian anyons or topological defects is a fundamental operation in measurement-only topological quantum computation. In topological superconductors, this operation amounts to a determination of the shared fermion parity of Majorana zero modes. As a step towards this, we implement a single-shot interferometric measurement of fermion parity in indium arsenide-aluminum heterostructures with a gate-defined nanowire. The interferometer is formed by tunnel-coupling the proximitized nanowire to quantum dots. The nanowire causes a state-dependent shift of these quantum dots' quantum capacitance of up to 1 fF. Our quantum capacitance measurements show flux h/2e-periodic bimodality with a signal-to-noise ratio of 1 in 3.7 $\mu$s at optimal flux values. From the time traces of the quantum capacitance measurements, we extract a dwell time in the two associated states that is longer than 1 ms at in-plane magnetic fields of approximately 2 T. These results are consistent with a measurement of the fermion parity encoded in a pair of Majorana zero modes that are separated by approximately 3 $\mu$m and subjected to a low rate of poisoning by non-equilibrium quasiparticles. The large capacitance shift and long poisoning time enable a parity measurement error probability of 1%.

cond-mat.mes-hall↗

arXiv2023

Optimal variable acceptance sampling plan for exponential distribution using Bayesian estimate under Type I hybrid censoring

In this study, variable acceptance sampling plans under Type I hybrid censoring is designed for a lot of independent and identical units with exponential lifetimes using Bayesian estimate of the parameter $\vartheta$. This approach is new from the conventional methods in acceptance sampling plan which relay on maximum likelihood estimate and minimising of Bayes risk. Bayesian estimate is obtained using squared error loss and Linex loss functions. Optimisation problem is solved for minimising the testing cost under each methods and optimal values of the plan parameters $n, t_1$ and $t_2$ are calculated. The proposed plans are illustrated using various examples and a real life case study is also conducted. Expected testing cost of the sampling plan obtained using squared error loss function is much lower than the cost of existing plans using maximum likelihood estimate.

math.ST↗

arXiv2023

Design of variable acceptance sampling plan for exponential distribution under uncertainty

In an acceptance monitoring system, acceptance sampling techniques are used to increase production, enhance control, and deliver higher-quality products at a lesser cost. It might not always be possible to define the acceptance sampling plan parameters as exact values, especially, when data has uncertainty. In this work, acceptance sampling plans for a large number of identical units with exponential lifetimes are obtained by treating acceptable quality life, rejectable quality life, consumer's risk, and producer's risk as fuzzy parameters. To obtain plan parameters of sequential sampling plans and repetitive group sampling plans, fuzzy hypothesis test is considered. To validate the sampling plans obtained in this work, some examples are presented. Our results are compared with existing results in the literature. Finally, to demonstrate the application of the resulting sampling plans, a real-life case study is presented.

stat.ME↗

arXiv2023

Design of generalized fuzzy multiple deferred state (GFMDS) sampling plan for attributes

. A sampling plan is a pilot tool for a supply and demand chain quality check strategy. These plans proved to be economically viable for the quality inspection processes but the uncertainty in the plan parameters challenged the reliability of the application of traditional acceptance sampling plans. This study proposes a generalized fuzzy multiple deferred state (GFMDS) sampling plan for attributes that consider the ambiguity in determining the exact value of the percentage of defectives in a batch. The performance measures have been derived and the plan is designed in terms of a minimum average sample number. A comparison study is done over the existing fuzzy acceptance sampling plans for attributes and a pertinent observation is made regarding the efficiency of the GFMDS scheme. The effect of inspection errors on the sampling procedure is analyzed and the drop in the acceptance criteria of the plan is observed corresponding to the intensified inspection errors. Several numerical examples are presented to validate the results

eess.SY↗

arXiv2023

Tunable Resonance and Electron-Phonon Coupling in Layered MoS2

Resonance Raman scattering, a very effective and sensitive technique for atomically thin semiconducting transition metal dichalcogenide, can be used to observe the phonons from the entire Brillouin zone. In addition to the significance of resonance effect on the Raman spectrum it may also be used to probe the electron-phonon coupling. Our study is devoted to understand the phonons in layered MoS2, especially for very low frequency range (i.e. below 100 cm-1), as a function of temperature under the resonance effect. Understanding the phonon-phonon and electron-phonon coupling and the effects of temperature on the Raman spectrum are the central points of the present study. We observe the anomalous softening and broadening of a very low frequency phonon mode P3 (~34 cm-1) at low temperature ( i.e below 150 K). We attributed the observed anomalous trend in frequency and linewidth of this low frequency phonon to the electron-phonon coupling. Furthermore, our work also highlights the temperature induced tuning of resonance condition via understanding the intensity of phonon modes as a function of temperature.

cond-mat.mtrl-sci↗

arXiv2022

InAs-Al Hybrid Devices Passing the Topological Gap Protocol

We present measurements and simulations of semiconductor-superconductor heterostructure devices that are consistent with the observation of topological superconductivity and Majorana zero modes. The devices are fabricated from high-mobility two-dimensional electron gases in which quasi-one-dimensional wires are defined by electrostatic gates. These devices enable measurements of local and non-local transport properties and have been optimized via extensive simulations to ensure robustness against non-uniformity and disorder. Our main result is that several devices, fabricated according to the design's engineering specifications, have passed the topological gap protocol defined in Pikulin et al. [arXiv:2103.12217]. This protocol is a stringent test composed of a sequence of three-terminal local and non-local transport measurements performed while varying the magnetic field, semiconductor electron density, and junction transparencies. Passing the protocol indicates a high probability of detection of a topological phase hosting Majorana zero modes as determined by large-scale disorder simulations. Our experimental results are consistent with a quantum phase transition into a topological superconducting phase that extends over several hundred millitesla in magnetic field and several millivolts in gate voltage, corresponding to approximately one hundred micro-electron-volts in Zeeman energy and chemical potential in the semiconducting wire. These regions feature a closing and re-opening of the bulk gap, with simultaneous zero-bias conductance peaks at both ends of the devices that withstand changes in the junction transparencies. The extracted maximum topological gaps in our devices are 20-60 $\mu$eV. This demonstration is a prerequisite for experiments involving fusion and braiding of Majorana zero modes.

cond-mat.mes-hall↗

arXiv2022

Revealing the Charge Transfer Dynamics Between Singlet Fission Molecule and Hybrid Perovskite Nanocrystals

Singlet fission process has gained considerable attention because of its potential to enhance photovoltaic efficiency and break the Shockley Queisser limit. In photovoltaic devices perovskite materials have shown tremendous progress in the last decade. Therefore combining the singlet fission materials in perovskite devices can lead to a drastic enhancement in their performance. To reveal the applicability of singlet fission processes in perovskite materials we have investigated the charge transfer dynamics from an SF active material 910 bis phenylethynyl anthracene to CH3NH3PbBr3 perovskite nanocrystals using the transient absorption spectroscopy. We observed a significant charge transfer from the coupled triplet state of BPEA to conduction band of CH3NH3PbBr3 in picosecond timescale. The observation of shortened lifetime in a mixture of BPEA and CH3NH3PbBr3 nanocrytals confirms the significant charge transfer between these systems. Our study reveals the charge transfer mechanism in singlet fission perovskite composite which will help to develop an advanced photovoltaic system.

cond-mat.mtrl-sci↗

arXiv2021

Unravelling the coupling between excitonic quasiparticles-electron-phonon and role of interlayer coupling in vertically and horizontally aligned layered MoS2

Excitonic quasi-particles, excitons/trions/bi-excitons, and their coupling with phonons and charge carriers play a crucial role in controlling the optical properties of atomically thin semiconducting 2D materials. In this work, we unravelled the dynamics of excitons/trions and their coupling with phonons and charge carriers in a few layers vertically and horizontally aligned MoS2. We observed trion signature up to the highest recorded temperature (330 K) in both systems and have shown that the dynamics of excitons/trions and their coupling with phonons and electrons are more affected in vertically aligned MoS2. A homogeneous linewidth broadening is observed with an increase in temperature. The linewidth broadening is attributed mainly to acoustic phonons in a low-temperature regime (<100 K). In contrast, acoustic and longitudinal optical phonons contributions to the linewidth broadening are observed at high temperature. We also observed the significant effects of interlayer coupling in both systems via understanding the temperature-dependent valence band splitting and trion binding energy. A decrease of 22 and 12% in valence band splitting with temperature rise is observed for the vertically and horizontally aligned MoS2, respectively, suggesting that the valence band splitting is affected more in the case of vertically than horizontally aligned. Furthermore, we also notice a significant thermal quenching in the intensity of the trion band than that of exciton bands, attributed to the small binding energy of the trion.

cond-mat.mtrl-sci↗

arXiv2021

Electron-Phonon Coupling, Thermal Expansion Coefficient, Resonance Effect and Phonon Dynamics in High Quality CVD Grown Mono and Bilayer MoSe2

Probing phonons, quasi-particle excitations and their coupling has enriched our understanding of these 2D materials and proved to be crucial for developing their potential applications. Here, we report comprehensive temperature, 4-330 K, and polarization-dependent Raman measurements on mono and bilayer MoSe2. Phonon's modes up to fourth-order are observed including forbidden Raman and IR modes, understood considering Frohlich mechanism of exciton-phonon coupling. Most notably, anomalous variations in the phonon linewidths with temperature pointed at the significant role of electron-phonon coupling in these systems, especially for the out-of-plane (A1g) and shear mode (E22g), which is found to be more prominent in the narrow-gaped bilayer than the large gapped monolayer. Via polarization-dependent measurements, we deciphered the ambiguity in symmetry assignments, especially to the peaks around ~ 170 cm-1 and ~ 350 cm-1. Temperature-dependent thermal expansion coefficient, an important parameter for the device performance, is carefully extracted for both mono and bilayer by monitoring the temperature-dependence of the real-part of the phonon self-energy parameter. Our temperature-dependent in-depth Raman studies provide a pave for uncovering the deeper role of phonons in these 2D layered materials from a fundamental as well as application point of view.

cond-mat.mtrl-sci↗

arXiv2021

Probing the Topological Surface States through Magnetoresistance and Ultrafast Charge Carrier Dynamics in (Bi/Sb)2Te3

Topological insulators with their topological protected surface states are highly promising quantum materials. In this article the micro-flakes of single-crystalline topological insulators Bi2Te3 and Sb2Te3 are explored through physical parameter measurement at low temperatures and thereby the charge carrier dynamics are investigated at 5K to study the various optical transitions related to these surface states. The magnetoresistance is experimentally investigated at temperatures of 5K and 100K for a field range of 1Tesla. The occurrence of the weak anti-localization effect predicts the presence of topologically protected surface states in the systems. Further, the ultrafast femtosecond transient reflectance spectroscopy is performed at different temperatures, varying from a room temperature (300K) to a low temperature of 5K, to find the TSS related transitions at low temperatures.

cond-mat.mtrl-sci↗

arXiv2021

Ion implantation in \b{eta}-Ga2O3: physics and technology

Gallium oxide and in particular its thermodynamically stable \b{eta}-Ga2O3 phase is within the most exciting materials in research and technology nowadays due to its unique properties, such as an ultra-wide band gap and a very high breakdown electric field, finding a number of applications in electronics and optoelectronics. Ion implantation is a traditional technological method used in these fields, and its well-known advantages can contribute greatly to the rapid development of physics and technology of Ga2O3-based materials and devices. Here, the current status of ion beam implantation in \b{eta}-Ga2O3 is reviewed. The main attention is paid to the results of experimental study of damage under ion irradiation and the properties of Ga2O3 layers doped by ion implantation. The results of ab initio theoretical calculations of the impurities and defects parameters are briefly presented, and the physical principles of a number of analytical methods used to study implanted gallium oxide layers are highlighted. The use of ion implantation in the development of such Ga2O3-based devices as metal oxide field effect transistors, Schottky barrier diodes, and solar-blind UV detectors, is described together with systematical analysis of the achieved values of their characteristics. Finally, the most important challenges to be overcome in this field of science and technology are discussed.

cond-mat.mtrl-sci↗

arXiv2020

Davydov Splitting, Resonance Effect and Phonon Dynamics in CVD grown Layered MoS2

We present a comprehensive temperature dependent Raman measurements for horizontally aligned CVD grown layered MoS2 in a temperature range of 4 to 330 K under resonance condition. Our analysis of temperature dependent phonon frequency shift and linewidth suggest a finite role of three and four phonon anharmonic effect. We observed Davydov splitting of the out-of-plane (A1g ) and in-plane (E12g ) modes, attributed to the weak interlayer interaction, and reflected in the appearance of additional modes with decreasing temperature for both 3 layers and few layers system. We also observed that the number of Davydov splitting components are more in few layers as compared to 3L MoS2, suggesting it increases with increasing number of layers. Temperature evaluation of the Raman spectra shows that the Davydov splitting, especially for A1g mode, is very strong and well resolved at low temperature. We note that A1g mode shows splitting at low temperature, while E12g mode is splitted even at room temperature, and that suggests to prominent role of A1g mode to the interlayer interaction. Further, the temperature dependence tuning of resonance effect is observed, via almost sixty fold increase in the intensity of the phonon modes at low temperature.

cond-mat.mtrl-sci↗

arXiv2020

Excited-state dynamics of structurally characterized crystal of SnxSb1-x

The topological behavior of heavy metal alloys opens a vast area for incredible research and future technology. Here, we extend our previous report about the superconducting properties of Sn0.4Sb0.6 along with the compositional variation of Sn and Sb in SnxSb1-x (with (X=0.5 and 0.6)) to study the detailed optical properties. Structural and morphological details of grown crystal are carried from the previous study. Further, the samples are excited by a pump of 2.61 eV with a broad probe of 0.77-1.54 eV in the NIR regime for transient reflectance ultrafast studies (TRUS) measurements. The differential reflectance profile shows an unprecedented negative magnitude, and the average power-dependent analysis of this negative trend has been analyzed. This article not only provides evidence of band filling phenomenon in the samples but also shows that with the variation of average power, there is a definite increase in the excited charge carriers, and thereby enhancing the band filling response. The estimated value of the bandgap between the band filled states and valence state is also determined from these studies. The nonlinear properties and bandgap analysis of the studied topological alloys and similar materials help in the advancement of various nonlinear optical applications.

cond-mat.mtrl-sci↗

arXiv2020

Metal Doping in Topological Insulators- A Key for Tunable Generation of Terahertz

The unique surface edge states make topological insulators a primary focus among different applications. In this article, we synthesized a large single crystal of Niobium(Nb)-doped Bi2Se3 topological insulator (TI) with a formula Nb0.25Bi2Se3. The single crystal has characterized by using various techniques such as Powder X-ray Diffractometer (PXRD), DC magnetization measurements, Raman, and Ultrafast transient absorption spectroscopy (TRUS). There are (00l) reflections in the PXRD, and Superconductivity ingrown crystal is evident from clearly visible diamagnetic transition at 2.5K in both FC and ZFC measurements. The Raman spectroscopy is used to find the different vibrational modes in the sample. Further, the sample is excited by a pump of 1.90 eV, and a kinetic decay profile at 1.38 eV is considered for terahertz analysis. The differential decay profile has different vibrations, and these oscillations have analyzed in terms of terahertz. This article not only provides evidence of terahertz generation in Nb-doped sample along with undoped sample but also show that the dopant atom changes the dynamics of charge carriers and thereby the shift in the Terahertz frequency response. In conclusion, a suitable dopant can be used as a processor for the tunability of terahertz frequency in TI.

cond-mat.mtrl-sci↗